The present invention relates to a slide table unit for retaining and linearly carrying a workpiece, a head of a tool, or the like.
A cylinder system in which a rod of a piston is supported by a hydrostatic bearing provided to a cylinder block is disclosed in Japanese Patent Application Laid-open No. 8-159106 and the like, for example. In the cylinder system, because it is necessary to provide means for increasing rigidity for resisting a moment load applied to on the rod and for suppressing rotation of the rod so as to allow the rod to slide stably, a whole device may be upsized. Especially, if a single piston rod is supported by hydrostatic bearings in a plurality of positions at a distance from each other so as to increase rigidity of the rod for resisting the moment load, upsizing of the device as a whole is inevitable.
It is a technical object of the present invention to solve the problems of the above cylinder system and to provide a compact slide table unit which has a simple and small structure and high rigidity for resisting a moment load applied to rods and in which rotation about the rods is not generated as well.
It is another technical object of the invention to provide the slide table unit with a structure that allows easy production of the above slide table unit.
To achieve the above objects, according to the invention, there is provided a slide table unit comprising a main body block having therein two rod support holes which are parallel to each other, a table for carrying a workpiece and disposed on the main body block for linear movement, hydrostatic bearings respectively provided in the rod support holes, and two rods respectively supported in noncontact states in the rod support holes through the hydrostatic bearings such that the rods can expand and contract.
Each the hydrostatic bearing is formed of a porous sleeve and has a function of supporting the rod in the noncontact state by compressed air supplied between an inside of the sleeve and the rod through the sleeve. One of the two rods projects outward from one end face of the main body block, the other of the two rods projects outward from the other end face on an opposite side of the main body block, projecting tip end portions of the rods are respectively connected to the table, base end faces of the respective rods are formed as pressure receiving faces, and the table is moved by alternately applying fluid pressure to the pressure receiving faces of the two rods to cause the rods to operate.
In the slide table unit of the invention having the above structure, because the table is moved by the two parallel rods supported by the hydrostatic bearings, rigidity for resisting the moment load is high and the table does not rotate about the rods. Moreover, the structure is simple and can be miniaturized.
Such a slide table unit can be used advantageously in a case in which the workpiece or a head and the like of a tool is retained and moved, e.g., a case in which a vacuum adsorbing portion for adsorbing the workpiece is provided to the table end to adsorb the workpiece while pressing the workpiece.
According to a concrete embodiment of the invention, the table includes two end plate portions facing the two end faces of the main body block from which the rods project and a connecting portion connecting the end plate portions such that the table is formed into a frame shape surrounding the opposite end faces and one side face of the main body block and each of the two end plate portions is connected to one of the two rods.
It is preferable that the table is fixed to one of the rods through a bolt and fixed to the other through an adhesive. In fixing the table to the rod through the adhesive, by bonding the table to the rod in a state in which compressed air is supplied to the hydrostatic bearings, it is possible to fix the table to the rod in a state in which the two rods are accurately positioned in parallel to each other and without displacements of cores in the two rod support holes of the main body block.
Dampers for absorbing shock in collision with stroke ends may be respectively mounted to the pressure receiving faces of the two rods.